Adjustable height system for wooden legged furniture

ABSTRACT

A threaded connection incremental height adjustment system for furniture having wooden legs that allows vertical alignment of extensions after tightening for leg extensions that are not circular in cross-section or are circular in cross-section but have patterns or designs that are desired to be aligned vertically.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX

Not Applicable.

BACKGROUND OF THE INVENTION

The present invention relates, in general, to the incremental height adjustment of furniture with wooden legs where the cross-sectional shape of the leg is not circular or where vertical patterns or designs on circular shapes would require alignment for visual reasons.

Prior art discloses threaded connections for incremental height adjustment in Crue, U.S. Pat. No. 7,278,687 B2 for bar stools, and in V. M. Winters, U.S. Pat. No. 3,232,253 for children's chairs. Both are limited to extensions having circular cross-sections without vertical patterns or designs on the exterior that would require vertical alignment. This limitation is due to the lack of a method to align the exterior of each extension piece while maintaining a tight threaded connection. The consequences of misaligning non-circular cross-section shapes would be a reduction in leg strength and unattractiveness.

Other systems elevate furniture by means of resting the legs on top of stacked interlocking spacer blocks of various sizes and shapes as in Robert Manatt Martin, U.S. Pat. No. 2,893,164; Williams, U.S. Pat. No. 5,615,429; Woods et al., U.S. Pat. No. 6,012,185; Keshavjee, U.S. Pat. No. 6,540,190 B2; Payne et al., U.S. Pat. No. 6,948,688 B1; Peterson, U.S. Design Pat. No. Des. 338,360; Abraham et al., U.S. Design Pat. No. D485,746 S; and Pehta et al., U.S. Design Pat. No. D498,412 S. These systems are relatively stable for small lateral forces; however none of these systems account for large vertical earthquake forces that could displace the legs from the top of the blocks and most are considered unattractive.

BRIEF SUMMARY OF THE INVENTION

The present invention is an easily installed and easily reversed system for the incremental height adjustment of furniture having wooden legs that are either not circular in cross-section or are circular in cross-section but have vertical patterns or designs that are desired to be aligned. Adjustment in height is accomplished by joining a 1 inch high wood block to the bottom of a leg through the use of threaded connections that are designed to allow alignment of the leg and block after the connection is tightened. Additional blocks are sequentially added to the first block and likewise aligned until the desired height is obtained, and a threaded end cap is added to the bottom of the last block. The blocks may then be finished by painting, staining, etc., as desired. The blocks will remain attached to the leg when subjected to large vertical earthquake forces and will remain properly aligned.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 illustrates a single extension block in accordance with an embodiment of the present invention.

FIG. 2 illustrates a cross-section through the vertical axis of a leg configured to an adjusted height with extension blocks in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a single extension block comprised of three parts; a wooden block 1, a threaded rod connector 2, and a threaded rod or stud bolt 3.

The wooden block 1 may be of any tree species, the characteristics of which may vary greatly and which may affect the size and shape of the other parts required to achieve the present invention. The wooden block 1 is generally one inch high with a length and width determined in conjunction with the size of the leg 4 to which it will attach and it may have patterns or designs upon its sides.

The threaded rod connector 2 is made of steel and the exterior of its horizontal cross-section is any shape except a circle.

The threaded rod or stud bolt 3 is made of steel and is compatible with the threaded rod connector 2 for the size and spacing of threads.

The extension block is formed by drilling a pilot hole through the center of the wood block 1 that is slightly smaller than the horizontal cross-section of the threaded rod connector 2, then pressing or driving the threaded rod connector 2 into the hole and seating it below the surface of the wood block 1. The non-circular cross-section of the threaded rod connector 2 will force the threaded rod connector 2 and wooden block 1 to rotate about their vertical axis in tandem; i.e., one cannot rotate relative to the other. A length of threaded rod 3 is then screwed into the threaded rod connector 2 and glued at the proper depth, or a stud bolt 3 may be screwed into the threaded rod connector 2 with the unthreaded portion of the stud bolt 3 located to control the depth of penetration.

The assembled extension block is then attached to a threaded rod connector 2 installed in the bottom of a leg either at the factory or by the end-user. Installation of the threaded rod connector 2 during the manufacturing process is preferred because they have more equipment choices and very experienced personnel. For good results, the threaded rod connector's 2 vertical axis must be aligned with the leg's 4 vertical axis and the threaded rod connector 2 glued or restrained in some manner at the proper depth in the leg 4. If the threaded rod connector 2 is not installed at the factory, the end-user can achieve satisfactory results using a hand-held drill and a drilling guide. A simple guide could be a wooden block supplied by the extension block manufacturer that is two inches thick and the same width and length as the supplied extension blocks with a pre-drilled hole along the guide's vertical axis. The user places the side of the guide with the hole against the bottom of the leg 4 and aligns the sides of the guide with the sides of the leg 4, then inserts a properly sized drill bit that has been marked with tape at three inches and drills a hole one inch into the leg along its vertical axis. The user places several drops of glue into the hole and drives the threaded rod connector 2 into the hole with a hammer and sets it below the wood surface using a hammer and punch or a hammer and screw driver.

Once the threaded rod or stud bolt 3 of the extension block is threaded into the threaded rod connector 2 in the leg 4, the extension block is rotated clockwise until it contacts the wood at the bottom of the leg 4. At this point the sides of the wooden block 1 will most likely not align with the sides of the leg 4 so additional force is applied in the clockwise direction to rotate the wooden block 1 until the sides align with the leg's 4 sides. The additional rotation of the wooden block 1 while it is bearing against the leg 4 will result in the threaded rod connector 2 being pulled upward toward the leg 4. This is a form of an Archimedes screw and the distance the threaded rod connector 2 moves is equal to the number of threads per inch times the number of rotations, or for twenty threads per inch at one half turn the distance moved is one fortieth of an inch. The amount of force necessary to rotate the wooden block 1 into an aligned position depends upon the surface area of the threaded rod connector 2 against the wooden block 1, the roughness of the threaded rod connector 2 surfaces, and the roughness, strength and moisture content of the wood in contact with the threaded rod connector 2.

Additional extension blocks may be added to the bottom of the first extension block and aligned as described above, one at a time, until the desired height is achieved. A threaded end cap 5 is added to the bottom of the last extension block to stabilize it. FIG. 2 illustrates the extension of a leg 4 using two extension blocks.

The above procedure is also used with extension blocks having a circular cross-section with patterns or designs on the exterior that are desired to be aligned vertically for aesthetic reasons.

The above procedure is reversible and the parts are reusable.

The final installation may be finished as desired by normal wood finishing techniques. 

1. A threaded connection incremental height adjustment system for furniture having wooden legs not circular in cross-section that allows for the vertical alignment of any height extension cross-section shape.
 2. A threaded connection incremental height adjustment system for furniture having wooden legs that are circular in cross-section that allows for the vertical alignment of vertical patterns or designs on each height extension. 